The field of the disclosure relates generally to electric motors, and more specifically, to systems and methods for sensing a line powering an electric motor.
As the world seeks more energy efficiency in operating electric motors, focus often turns to replacing lower efficiency permanent split capacitor (PSC) motors and induction motors with electronically commutated motors (ECMs). When retrofitting and/or designing an ECM, it is often desirable to use the relay power outputs that have been used to drive the PSC to connect with control input pins of the ECM. In this manner, a controller that was originally used to drive the PSC may be used to directly control the ECM. However, at least some known PSC controllers included either electromechanical relays with snubber circuits or used solid state relays (SSRs). This presents a potential problem with the high impedance control input lines on the ECM. The leakage current of the snubber or the SSR may cause a false RUN signal to be sent to the ECM. In this case the motor simply runs all the time, instead of when the relay is activated, resulting in increased operating costs and lowering efficiency of the motor.